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Pesticides & male infertility: Harm from the womb through adulthood -- and into the next generation

Human reproduction is a delicate bio-chemical process, guided at every step by powerful hormones. Reproductive health involves everything from the physical ability to reproduce to the many behavioral and developmental effects of sex hormones.

This finely tuned system is under threat, and male fertility appears to be particularly at risk. Worldwide, sperm counts are down and infertility rates are up. The Association of Reproductive Health Professionals highlights concerning trends[i] in male reproductive health, including:

Rising rates of testicular cancer

Falling sperm counts

Decline in testosterone levels

Fewer males being born

Increases in certain types of birth defects

Science tells us that pesticides and other chemicals are at least partly to blame. Endocrine disrupting chemicals are particularly adept at interfering with reproductive health, even when exposure levels are extremely low. Some of these chemicals are structurally similar to human hormones, and can block (or put into overdrive) the body's natural system of biological signals.

An infant in the womb is particularly vulnerable to such disruption, as hormones are busy regulating the differentiation of cells and development of organs. Infants exposed to a triggering chemical just when the reproductive organs are forming — or the brain developing, or immune system coalescing — can experience harm that can play out over the course of a lifetime. The Endocrine Disruption Exchange has a compelling online tool[ii] illustrating the vulnerabilities of a fetus at various stages of development.

Scientists from the national Endocrine Society explain why the timing of exposure is so important:

...thereare critical developmental periods during which there may beincreased susceptibility to environmental endocrine disruptors.In those cases in which disruption is directed toward programmingof a function, e.g., reproductive health, this may interferewith early life organization, followed by a latent period, afterwhich the function becomes activated and the dysfunction canbecome obvious.[iii]

In other words, exposure to certain chemicals when an infant's reproductive system is developing can completely derail the process. But the effects won’t become evident until years later, when problems arise during puberty or when trying to conceive.

Adult exposures to pesticides can influence male fertility as well. Authors of a 2013 review published in Toxicology[iv] examined 17 studies published between 2007 and 2012, all exploring how environmental and occupational exposures to pesticides affect semen quality. Some studies looked at individual chemicals (such as DDT and hexachlorocyclohexane), others looked at classes of pesticides such as organophosphates and pyrethroids. The majority of these studies (15 of the 17) found significant links between pesticide exposure and lower semen quality, with decreased sperm concentration the most commonly reported finding.

Links between pesticide exposure and damage to men's reproductive ability are hardly new. The classic example is Dow's fumigant Nemogen (DBCP), which sterilized workers both in the California factory where it was produced and in the Nicaraguan banana plantations[v] where it was heavily applied. And exposure to current-use pesticides like atrazine and diazinon[vi] has also been shown to undermine sperm viability and function.

Pesticides can damage the male reproductive system in a number of ways. Some chemicals can kill or damage cells; if these are sperm cells, infertility can result. Others alter DNA structure, causing gene mutations that may result in birth defects or an inability to conceive. And still others cause what are known as "epigenetic" effects, meaning they change the way genes are expressed.[vii]

It’s been known for some time that pollutants can strip or add chemical tags to DNA, locking the expression of these genes on or off and changing how they function. These changes are called “epigenetic tags,” and have been linked to various health effects including death of sperm-forming cells.

Perhaps most sobering of all, emerging science shows that these genetic changes can be passed from one generation to the next. Recent studies from Spain[viii] and Washington state[ix] found that exposure to some chemicals can override the genetic “reset button” designed to protect a developing fetus from such changes. These trans-generational effects give new urgency to efforts to reduce our use of and exposure to harmful pesticides.

Comments

Andres fernandez said ..

I am writing from costa rica where I have lived for two years next to pesticide drenched pineapple and banana plantations. I have been raising free range chickens and it is now clear that all the males born at my place are totally infertile. It is so obvious it is alarming. God only knows what the chemicals are doing to people who live here and the workers who labor all day spraying and being sprayed with diverse poisons. Hopefully I will be moving very soon but there are people born here who cannot escape so easily.

October 12, 2016

Fabiha Nowshin said ..

The article was good .I've learnt something new from here.I think our farmers (Bangladesh) are unconcious about the harmful effects of pesticides on their reproductive health.So I'll try my best to raise awareness about this matter whatever I've learnt from this article. 😊

June 25, 2016

LH said ..

Great article in Feb. 10 New Yorker about the company Syngenta, that makes atrazine, a common corn herbicide, trying to harass and suppress a black researcher's studies that showed frogs exposed to atrazine had multiple deformed testes or both testes and ovaries.